1. Technical Field of the Invention
The present invention relates to a projection image display apparatus equipped with an image generation part in which a plurality of mirror elements are arranged, the mirror elements moving between an on-position at which illumination light from an illuminating optical system is reflected toward a projection optical system and an off-position at which the illumination light is reflected toward the outside of the projection optical system, whereby on-light is reflected from the mirror element located at the on-position constituting an image.
2. Description of the Related Art
A DMD projector provided with a DMD (digital micro mirror device) as the image generation part has been known. The DMD is composed by arranging, in a matrix state, many light reflection angle variable mirror elements capable of being changed between the on-position at which the received illumination light is reflected toward the projection optical system and the off-position at which the illumination light is reflected toward the direction out of the projection optical system. The projected image is composed by the group of the on-light reflected from the mirror element located at the on-position.
The DMD projector has a high optical utilization efficiency since the DMD projector uses the simple light reflection due to the mirror element. Therefore, as compared with an LCD projector, the DMD projector has an advantage that the high-brightness of the projection image can be realized. On the other hand, the DMD projector has a problem in that the off-light reflected from the mirror element located at the off-position is mixed with the on-light and the quality of the projection image is reduced. Therefore, devices are disclosed, in which a shielding film and a light absorbing member are provided between the DMD and the projection optical system, and the off-light from the DMD is absorbed (see JP-A-9-98442 and JP-A-9-96867).
However, the related art devices absorb the off-light, and flat light reflected between the on-light and the off-light is not considered. The flat light is reflected light from a cover glass or the like for mainly protecting the DMD, and a problem exists in that the flat light is mixed with the on-light and thereby the brightness unevenness is generated on the projection image.